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Old 27th April 2014, 08:07 PM   #1
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Default Reproducing a 16Hz pipe organ note

For reasons I wonít bore you with I need to build a speaker system to accurately reproduce the 16Hz sound of a 32í pipe organ bass pipe in our church. Our auditorium seats 400 and I need 125db at 1 meter. A TH design can do this with enough cabinets of sufficient size (250-300 litres and 16 feet of horn length).


Now hereís the rub. Due to the roomís design, the only place to house these monsters is in the current speaker chamber of the electronic organ weíre trying to replace. The speaker chamber is 8 feet above the choir loft in the middle of the stage wall. It has an area of 4 by 9 with a 7 foot ceiling and is open to the auditorium.


Iíve been working in Hornresp and have a couple TH designs which I think will work. At these frequencies xmax goes through the roof quickly.


Is a TH the best design for this application given the size constraints given? Iíve been working with a longer version of the Volvotreter 20Hz cabinet with a double fold to make the cabinet 4-5 feet tall. It can also be done with a longer version of Jbellís stadium horn (as if it wasnít big enough already).


Is There a better design for this application? Iíve read so many great threads about TH design, I just want to make sure Iím not missing something by not focusing enough on other designs.


And I use to think that 40Hz was low enough!!


Steve
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Old 27th April 2014, 08:31 PM   #2
SirByrd is offline SirByrd  United States
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Pi Speakers, Subwoofers, 12Pi basshorn subwoofer
This might work, it's not rated down to 16Hz but it has enough max SPL that you could probably use it at 16Hz and get close.
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Old 27th April 2014, 09:22 PM   #3
Cask05 is offline Cask05  United States
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Quote:
Originally Posted by Old Ears View Post
For reasons I won’t bore you with I need to build a speaker system to accurately reproduce the 16Hz sound of a 32’ pipe organ bass pipe in our church. Our auditorium seats 400 and I need 125db at 1 meter. A TH design can do this with enough cabinets of sufficient size (250-300 litres and 16 feet of horn length).


Now here’s the rub. Due to the room’s design, the only place to house these monsters is in the current speaker chamber of the electronic organ we’re trying to replace. The speaker chamber is 8 feet above the choir loft in the middle of the stage wall. It has an area of 4 by 9 with a 7 foot ceiling and is open to the auditorium...

...Is a TH the best design for this application given the size constraints given?

...Is there a better design for this application?
It would be nice to know the approximate dimensions of the room itself, not just the area where the sub(s) will reside. A TH design will be almost perfect since most organs using 32' ranks don't require impulse response. Note that TH designs have a little bit of a "precursor" pulse - just like 32' pipe ranks have when the wind chest is first opened to the pipe, creating a "pip" precursor pulse.

Here is a design that will do it: Dual 8" tapped horn = TH-SPUD I've got two of these in my listening room in the room's front corners (I'd recommend at least two units), and here is the composite response (the red trace):

Click the image to open in full size.

Note that my drywall corners are the real limiting factor here - the corners need to be much stiffer to achieve smooth in-room response below 20-25 Hz.

Recommend using Russian ("Baltic") birch ply, not the other cheaper stuff. Also note that you need to assemble the pieces within a day or so after cutting since this plywood has a tendency to move over time if not assembled.

Chris

Last edited by Cask05; 27th April 2014 at 09:36 PM. Reason: Added TH appropriateness answer
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Old 27th April 2014, 10:15 PM   #4
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Are you sure that the ONLY place for the speakers is where you specified?

The upper corners of the room are unavailable for some reason?
How about the basement (does it have a crawl space or basement?)

Also look at some of the Danley designs, they may have one that is appropriate.

And, you said the "16Hz" sound, are you JUST wanting the 16Hz note or other notes??

There may well be a way to do this without ever actually reproducing a 16Hz note - the Waves company has an algorithm that does a trick that makes the ear hear a fundamental that is not actually present.

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Old 27th April 2014, 11:16 PM   #5
xrk971 is offline xrk971  United States
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Let me get the specifics straight: the sound has to come from a 4x9x7 ft chamber located 8 ft above stage on front wall; how high is at the front wall? The simulation will have to take into account the wall or ceiling/floor height into, and in all likelihood you will get some room gain near 16 Hz. When space is a constraint but budget is not - it may make sense to have a big stack of 15 in subs in sealed chambers and pump lots of watts with EQ into them. A TH should be able to fit In there too. Do you have a budget limit on amps and drivers?

Last edited by xrk971; 27th April 2014 at 11:19 PM.
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Old 27th April 2014, 11:24 PM   #6
sreten is offline sreten  United Kingdom
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Hi,

I have a problem with anyone coming here and asking questions
about what is effectively a professional installation and about
a subject people know little about and vague questioning.

Your replacing an electronic organ that has a real 16Hz stop ?
How did it do it ? And replacing it with what ? And why ?

rgds, sreten.
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Old 27th April 2014, 11:36 PM   #7
jbell is offline jbell  United States
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I will question an electric organ patch that actually puts out 16hz. Yes, I know the note for C0 is there in your patch, but it is typically reproduced (even with pipes, not just electronics) by beating a C1-G1 together.

Combination tone - Wikipedia, the free encyclopedia

Can you verify that you are actually reproducing a 16hz ??
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Old 27th April 2014, 11:41 PM   #8
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Quote:
Originally Posted by bear View Post
Are you sure that the ONLY place for the speakers is where you specified?

The upper corners of the room are unavailable for some reason?
How about the basement (does it have a crawl space or basement?)

Also look at some of the Danley designs, they may have one that is appropriate.

And, you said the "16Hz" sound, are you JUST wanting the 16Hz note or other notes??
_-_-
The room has none of the preferred locations available. The roof is peaked, 40ft high, with an easy angle to the 10ft side walls. All corners have doors and aisle-ways, no clear walls, the floor is a poured slab, and the front of the stage has stairs all the way across. DSL does have speakers that would work, but we could build for almost 10% of the cost.

I should have also said that these would also be integrated into the existing sound system as PA subs. Thanks to MiniDSP I could feed the amps from both the "organ" and the PA with different high pass and limiters. So they need to be 15-80Hz or as high as the design will allow.

I guess my main question is does a TH design gives me the most sound per cubic litre?

Steve
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Old 27th April 2014, 11:45 PM   #9
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Quote:
Originally Posted by jbell View Post
I will question an electric organ patch that actually puts out 16hz. Yes, I know the note for C0 is there in your patch, but it is typically reproduced (even with pipes, not just electronics) by beating a C1-G1 together.

Combination tone - Wikipedia, the free encyclopedia

Can you verify that you are actually reproducing a 16hz ??
No I can not. If this is correct then I'll just build 4 stadium horns and be done with it.

Steve
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Old 27th April 2014, 11:52 PM   #10
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Quote:
Originally Posted by Old Ears View Post
For reasons I won’t bore you with I need to build a speaker system to accurately reproduce the 16Hz sound of a 32’ pipe organ bass pipe in our church. Our auditorium seats 400 and I need 125db at 1 meter. A TH design can do this with enough cabinets of sufficient size (250-300 litres and 16 feet of horn length).


Now here’s the rub. Due to the room’s design, the only place to house these monsters is in the current speaker chamber of the electronic organ we’re trying to replace. The speaker chamber is 8 feet above the choir loft in the middle of the stage wall. It has an area of 4 by 9 with a 7 foot ceiling and is open to the auditorium.


I’ve been working in Hornresp and have a couple TH designs which I think will work. At these frequencies xmax goes through the roof quickly.


Is a TH the best design for this application given the size constraints given? I’ve been working with a longer version of the Volvotreter 20Hz cabinet with a double fold to make the cabinet 4-5 feet tall. It can also be done with a longer version of Jbell’s stadium horn (as if it wasn’t big enough already).

Is There a better design for this application? I’ve read so many great threads about TH design, I just want to make sure I’m not missing something by not focusing enough on other designs.
Steve,

TH will give you what you need with the minimum of drivers and power, though with the space available a FLH (front loaded horn) would also work fine too.
The Volvoreter type cabinet is an easy build, multiples with a longer horn would do 125 dB at 16 Hz. A longer version of Jbell’s stadium horn is a more difficult build.

One of Josh Ricci’s Gjallerhorn (also a rather difficult build using an expensive driver) would "get er done",(within .7 dB) at 2 meter, ground plane, outdoors it measures:
10hz 90.2db
12.5hz 105.2db
16hz 118.3db
20hz 122db
25hz 124.9db
31.5hz 125.8db
40hz 128.4db
50hz 127.2db
63hz 130.2db
80hz 130.9db
Add 6 dB for one meter equivalent, and you may pick up some room gain down low too, though unless you have taken room measurements with a sub placed in the actual speaker chamber place, don't count on it.

At only about 103 dB SPL at 15 Hz the sheet rock wall flaps in the corner the sub is located in my control room. You may experience some structural damage to the building if a sustained 125 dB low note happens to coincide with wall or ceiling resonance, falling plaster is an unwelcome musical accompany .

P.S.
TH do not have as much output per cubic liter as bass reflex, but can use half the drivers and power to achive the same levels. In your case, you have plenty of room for a 125 dB TH.
Also, the output of your organ can easily be seen with any of the many free RTA programs available, it would be prudent to check it out before contemplating the cabinet design. A single BC 18SW115-4 loaded Keystone sub could do around 125 dB at 32 Hz.

Art

Last edited by weltersys; 28th April 2014 at 12:00 AM.
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